1. Field of the Invention
This invention relates to the art of operating cells that are used for the electrolysis of brine to produce chlorine and caustic, and in particular to such cells wherein a diaphragm divides the cell into anolyte and catholyte portions, with the diaphragm being of relatively hydrophobic material such as highly crystalline polytetrafluoroethylene. It concerns a method for preparing a diaphragm for use before its insertion into such a cell, and in particular, it concerns adequately wetting the diaphragm prior to use.
2. Description of the Prior Art
The operation of diaphragm-type electrolytic cells to produce caustic and chlorine is well known to those skilled in the art. Although it has been usual to use asbestos for diaphragms of such cells, there has recently been a trend to change to different diaphragm materials, such as crystalline polytetrafluoroethylene, because of the considerable occupational-hazard problems encountered in the manufacture of asbestos and the expense of meeting them. The crystalline polytetrafluoroethylene material is quite satisfactory as a diaphragm material, except for its drawback of being rather hydrophobic and consequently tending to be difficult to wet, or tending to dewet while in service. Although, in operating with very small cells on a laboratory scale, it is convenient to use acetone as a means of wetting a highly crystalline polytetrafluoroethylene diaphragm, such a practice is not useful with respect to the wetting of a large or moderately large diaphragm, of the kind that is encountered in a pilot-plant or commercial-scale unit. Acetone is volatile, and it often escapes before the diaphragm is completely installed. It is known that other means are required in order to solve the problems thereby presented, and the published patents concerning the use of polytetrafluoroethylene as a diaphragm material in the manufacture of caustic and chlorine by the electrolysis of brine do not present any particular solutions to the problem above-indicated.